Unfortunately it's not 'one' issue. An 'AI' is a huge library of functions, not one neat little 'run AI' unit in the program.
So there's not likely to be a 'patch' (singular) that fixes all or even a large number of the problems with the AI. It's being fixed, bit by bit, but very slowly because there is so much to cover. I think a large part of the problem is that the game is so customizable. The AI has to be able to handle a much wider range of circumstances than something like the the Master of Orion I/II AI or even the SE III had to handle, and both the Master of Orion I/II AI and SE II AIs were pretty good.